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Measuring & Mapping

Where, how far, and how much? People have invented an astonishing array of devices to answer seemingly simple questions like these. Measuring and mapping objects in the Museum's collections include the instruments of the famous—Thomas Jefferson's thermometer and a pocket compass used by Meriwether Lewis and William Clark on their expedition across the American West. A timing device was part of the pioneering motion studies of Eadweard Muybridge in the late 1800s. Time measurement is represented in clocks from simple sundials to precise chronometers for mapping, surveying, and finding longitude. Everyday objects tell part of the story, too, from tape measures and electrical meters to more than 300 scales to measure food and drink. Maps of many kinds fill out the collections, from railroad surveys to star charts.

A declinometer measures the horizontal angle between the geographic and magnetic poles of the earth (also known as the declination, or variation, of the magnetic needle). This particular form was introduced by H. P. Gambey of Paris in the 1830s and remained popular in France throughout the century. This example was purchased in France and was probably produced there as well. It consists of a heavy stone base, a bar magnet supported by a thread, and microscopes at either end to read the magnet's position.

In the late eighteenth century, French scientists introduced a new system of weights and measures known as the metric system. Units of length, volume and mass were interrelated. A cube 10 centimeters on a side (1000 cubic centimeters) was defined to have a volume of one liter. The weight of one liter of pure water was called a kilogram.

These eleven brass cylinders have weights ranging from two grams to 1000 grams, or one kilogram. They are stamped in French with their weight – 2 GRAM, 5 GRAM, 10 GRAM (2 weights), 20 GRAM, 50 GRAM, 100 GRAMMES (2 weights), 200 GRAMMES, 500 GRAMMES, 1 KILOGRAMME. Each weight has a knob at the top for lifting. The weights have no maker’s mark.

This graphometer is marked "Delure A Paris" and dates from the early 18th century.The semicircle is graduated to single degrees, numbered clockwise and counterclockwise, and read by diagonal scales at either end of the alidade to 10 minutes.

A graphometer consists of a graduated semicircle with a pair of sight vanes at either end, and a movable alidade with another pair of sights at either end. The form was introduced in Philippe Danfrie, Déclaration de l’usage du graphomètre (Paris, 1597), and was always popular in France. Many graphometers have an inset magnetic compass. Most graphometers are made of brass, but some American ones are made of wood. Some 19th-century graphometers had telescopes rather than open sights. Graphometers were also known as semi circles or semicircumferentors.

Over the years, enormous ingenuity has been directed to the problem of designing a barometer that could be safely moved from one place to another. One solution was to have the cistern full during transport, and mechanically expanded to a proper size for actual use. This example, which is of that sort, is marked “Tonnelot à Paris.” The signature refers to Jules Tonnelot, a Parisian who showed his meteorological instruments at the international exhibitions held in 1878, 1889 and 1900.

This magnetic compass has a paper scale, a metal needle, a wooden case, and a glass cover. The scale is graduated every 10 grads and marked every 20, with a total of 400 grads in the circle. Folding metal sights are attached to the north and south edges. A plumb bob stored in the north edge of the case can be suspended from the east edge.

From ancient times, mathematicians described a right angle as having ninety degrees. In the 1790s, the French introduced a right angle of one hundred decimal degrees or grads. Instruments divided this way were available in France and in the United States into the 20th century.

In 1847, a French hydraulic engineer named André G. A. Baumgarten published an account of his work with a horizontal-axis current meter that was based on the form described by Reinhard Woltmann, a German hydraulic engineer, in 1790. Lerebours et Secretan (fl. 1845-1855), a prominent instrument firm in Paris, began offering a “Moulinet de Woltmann” soon thereafter, noting that this form was used in the hydraulic service of the Ponts et Chausées, the national agency in charge of bridges and roads.

The “Lerebours et Secretan / à Paris” signature on this example dates from the period 1845-1855. The instrument came from the Proprietors of the Locks and Canals, the corporation that developed water transportation along the Merrimack River, and water power for the town of Lowell, Massachusetts. James B. Francis probably acquired it shortly after having been named manager of that organization. It came to the Smithsonian in 1956, and was restored by the U.S. Geological Survey in 1958.

Clemens Herschel opined in 1869 that “The best instrument to measure the velocity of the current at any point has generally been thought to be the so-called Woltmann wheel, or tachometer.” James B. Francis did not mention an instrument of this sort in the first (1855) edition of his Lowell Hydraulic Experiments, but in 1868 he noted that “Woltman’s mill, or tachometer, has been much used for this purpose, but to insure correct results, its application is one of much delicacy, and in our large channels would require much time.”

The “Moulinet de Baumgarten” is a horizontal-axis instrument based on the form that had been introduced by a German hydraulic engineer named Reinhard Woltman, and modified by a French hydraulic engineer named André G. A. Baumgarten. This example is 17 inches long, with a three-inch diameter wheel and a four-blade rudder. It was probably made in France in the 1850s or 1860s. A tag on the box reads “LOCKS AND CANALS 66 BROADWAY LOWELL MASS.” The Proprietors of the Locks and Canals, the corporation that developed water transportation along the Merrimack River and water power for the town of Lowell, Mass., gave it to the Smithsonian in 1956.

The semicircle of this graphometer is graduated to single minutes, numbered clockwise and counterclockwise, and is read by verniers at either end of the alidade to 6 minutes. The "Meurand à Paris” signature refers to an instrument maker who worked in Paris in the latter years of the 18th century.

This sextant belonged to Weston College in Weston, Massachusetts, and probably dates from the third quarter of the 19th century. It has a brass frame. The inscription on the arc reads "J. & A. Molteni à Paris." The silvered scale is graduated every 10 minutes from -5° to +168° and read by vernier with tangent screw and magnifier to 10 seconds of arc. The Molteni family was in business in Paris from 1782 to about 1900, making a wide variety of mathematical instruments.

Wesleyan University was founded in 1831, and during the next several years it purchased some $6000 worth of scientific apparatus, much of it made in Paris. This dip circle is from that period. It is marked "Lerebours à Paris" and "W.U. No. 2." The vertical circle is suspended from a brass hook attached to a rotating knob, and so can be turned in any direction. The horizontal circle, on top, is graduated to single degrees. The vertical circle is graduated to 30 minutes; the glass covers are missing.